B or B+ evolve or mutate

Is there a way to evolve or mutate b or b+

I think you can only evolve an A, but mutation is a possibility. Mutation however is really rare and I've yet to see it really work, but you can always try.

What means mutation?
Does that mean a skill appear to a monster, which didn't have skill?
Or does mutation mean something else?

If you look at the menu bar on the bottom there's a help button and if you scroll through the options one of the help categories will be mutation. Mutation from what I'm gathering from the help thing is basically mixing two monsters and hoping an advanced/different one pops out on the other end, but it only occurs if you sacrifice one monster, not a whole slew of them.

if you sacrifice ONE monster in order to level up another one (example goblin lvl 1), there is a really LOW chance that instead of getting a level 2 monster, you'll get a completely random other monster.
It's unclear what is the chance of this to happen, and if there are conditions of any kind to have good monsters.

I sacrificed 2 Dark Elf Blades (C) for lulz and got a poison mist spider B+...o_O;